Portable refrigerator



FIG. 1 is a front perspective view from above of a portable refrigerator, showing my new design;

FIG. 2 is a front view thereof;

FIG. 3 is a rear view thereof;

FIG. 4 is a top plan view thereof

FIG. 5 is a bottom plan view thereof;

FIG. 6 is a left side view thereof; and,

FIG. 7 is a right side view thereof. 

The ornamental design for a portable refrigerator, as shown and described. 